Question

On heating blue coloured powder of copper (II) nitrate in a boiling tube, copper oxide, a colourless gas X and a brown gas Y is formed.
1.) Identify the gases X and Y.
2.) Identify the type of chemical reaction involved.
3.) Write a balanced chemical equation of the above reaction.

Answer 1

Hint: When copper nitrate is heated, it loses the water molecule, and then when it is further heated, it decomposes further to give a brownish and a colorless gas.

Complete step by step solution:
The chemical formula of copper (II) nitrate is $Cu{(N{O}_{3})}_{2}$. It is a blue-colored solid powder and the anhydrous form of this compound forms deep blue-green crystals.
The heating of copper (II) nitrate, results in the loss of a water molecule. When this anhydrous copper (II) nitrate is further heated it gives a black residue of copper oxide and also gives out a brown gas i.e., of nitrogen dioxide and a colorless gas which is of oxygen. Therefore, the gases X and Y are oxygen and nitrogen dioxide respectively.
In this reaction, as copper (II) decomposes to form copper oxide, nitrogen dioxide gas, and oxygen gas as products, therefore, it is a decomposition reaction.
The balanced chemical equation involved in this reaction is given below:
$2Cu{ (N{ O }_{ 3 }) }_{ 2 }(s)\quad \xrightarrow [ Heat ]{ } \quad 2CuO(s)\quad +\quad \underset { Reddish-brown\quad gas }{ 4N{ O }_{ 2 }(g) } \quad +\quad \underset { Colorless\quad gas }{ { O }_{ 2 } }$

Note: The copper nitrate is a very toxic chemical for aquatic life. The nitrogen dioxide gas that is formed in this reaction is acidic in nature. Therefore, its pH will be in the range of 0 to 7.